Method for tandem gas metal arc welding, and welding torch and welding apparatus used therefor

Abstract

The present invention provides a method for tandem gas metal arc welding using a leading electrode and a trailing electrode, wherein a shielding gas for the leading electrode is a two-component mixed gas containing argon and carbon dioxide, or a three-component mixed gas containing argon, carbon dioxide, and oxygen; a shielding gas for the trailing electrode is argon, a two-component mixed gas containing argon and carbon dioxide, a two-component mixed gas containing argon and oxygen, or a three-component mixed gas containing argon, carbon dioxide, and oxygen; and the concentration of carbon dioxide in the shielding gas for the trailing electrode is lower than the concentration of carbon dioxide in the shielding gas for the leading electrode.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for tandem gas metal arc welding (GMA welding) in which a deposition rate per one weld pass can be increased by moving two electrodes at the same time, and a welding torch and a welding apparatus used in this welding method.[0002]Priority is claimed on Japanese Patent Application, No. 2006-211093, filed on Aug. 2, 2006, the contents of which are incorporated herein by reference.BACKGROUND ART[0003]Decreasing cost is required in many fields such as a field in which Wick plates used in construction equipment and bridges, etc. are welded, and a field in which thin plates used in an automobile are welded. Therefore, a tandem GMA welding method which can weld with a high efficiency has been used.[0004]The tandem GMA welding is a method in which two welding wires used as electrodes are used, and two arcs are generated at the same time to weld. The main advantages of the tandem GMA welding are that the welding speed can be incr...

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Benefits of technology

[0024]According to the method for tandem GMA welding of the present invention, it is possible to decrease the amount of the spatter generated dung welding without a decrease of the weld penetration depth by using shielding gases which are suitable for the leading electrode and the trailing electrode. Thereby, it is possible to decrease the load for removing the spatter, and decrease the cost of welding.

[0020]In order to achieve the object, the present invention provides a torch for tandem GMA welding, wherein the torch is used in the method for tandem GMA welding, and the torch has plural electrodes inside a nozzle, and a partition for preventing to mix a shielding gas for a leading electrode and a shielding gas for a trailing electrode.

[0029]In addition, when the protection cover is arranged on the welding torch, the shielding gas nozzle is attached to the protection cover, and the shielding gas is supplied from the shielding gas nozzle, it is possible to block the molten pool from the atmosphere. As a result, it is possible to decrease welding defects such as oxidation, nitridation, and blow-holes.

[0030]Furthermore, the welding direction for the torch is arbitrarily changed, and the leading electrode and the trailing electrode are replaced with each other in practical welding. The welding apparatus according to the present invention has a gas switching device for supplying the shielding gas for the leading electrode to an electrode to be the leading electrode, and the shielding gas for the trailing electrode to an electrode to be the trailing electrode, depending on the change of the welding direction. Thereby, it is possible to obtain the equivalent freedom obtained by using the shielding gases having an identical composition for the leading and trailing electrodes without subjecting to restriction by the welding direction.

Problems solved by technology

However, since an attractive force between the two arcs is generated, a shape of a droplet is not fixed and here is a tendency for the separation properties of the droplet to be inferior.

Therefore, a larger amount of the spatter is generated compared with a conventional GMA welding method using one welding wire.

A great deal of time is necessary to remove the spatter attached on weld beads, and there is a problem of an increase of welding cost.

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